Sometimes it is necessary to calculate a lifetime for some devices, things. Usually, a lifetime calculates in full months, for example, to check a warranty or guaranty period. Excel proposes a very useful formula that can help calculate that time.

For some projects or tasks, you might need to calculate how many days, months, or years left to some date or how many days, months, or years passed from some date till today. Excel proposes a very useful formula that can help you to calculate that very fast.

When you plan a project, you can need to calculate a number of workdays or full workweeks between the start and end dates, or how many workdays or workweeks left/passed. This tip is about an easy and fast way of calculation of full workweeks for weeks from Monday to Sunday.

When you plan a trip, project, etc. you can need to calculate a number of days or weeks between the start and end dates, or how many days or weeks left/passed. This tip is about an easy and fast way of complete weeks calculation.

When calculating the difference between two dates, you may want to exclude weekends and holidays. Excel proposes a standard formula for calculating the number of workdays for standard, five-day workweek. Also, Excel proposes a formula for calculating the number of workdays for different five-day workweek or six-day workweek.

From time to time, you need to count days of week between two dates or in some date range (see How to count days of week in the range of dates). Excel proposes different formulas to work with data. It is easy to create the formula you need for this task:

From time to time, you need to count days of week in some date range or between two dates (see How to count days of week between two dates). Excel proposes different formulas to work with data. It is easy to create the formula you need for this task:

When calculating the difference between two dates, you may want to exclude weekends and holidays. You can see how to calculate the number of Working Days between two dates for the usual, standard working week where weekends are Saturdays and Sundays.

If you use formulas in Excel, you often can see messages such as #VALUE! or #DIV/0!. Most of the time, this means you need to check the source of the error and fix it, but sometimes a formula error simply means that the data used by the formula is not yet available.

By default, when you work in Excel, it automatically identifies all issues, such as incorrect data in the cell, problems with formulas, etc. So, you see green triangles (by default) shown in the top left corner of these cells.